PSYC11H3 Lecture Notes - Lecture 6: Sports Experts, Prediction Market
Document Summary
Problems with group deliberation: groups are re-affirming, some opinions are not voiced, opinions are not independent. Example: people at a regional fair estimated the weight of an ox. Example: baseball prospectus is a baseball website for geeks, at the beginning of some seasons, they offer a competition among all of their members to predict the win totals of each of the 30 baseball teams. How did the average perform: correlations between final win totals and various predictors in for 2006 season, espn sports experts: +. 64, las vegas: +. 62, baseball prospectus members: +. 68. How did each group do against vegas: 2006 espn sports experts: 51. 9, 2006 baseball prospectus members: 73. 3% Absolute deviation = guess true answer. Judgments are often unreliable and susceptible to random errors: averaging cancels out random errors. Individual judgments are biased by one"s own unique perspective or tendencies: group discussion amplifies such biases, averaging cancels them out.
